I have a Hyundai h 100 2007 100 000 km. How do I trace a knock

Whilst I was driving on the freeway the vehicle developed a knock and then started to lose power.I pulled over and switched off. Half hour later I restarted and continued on my journey. 5 km further the knock came back and once again started losing power, stopped the vehicle and got towed. The next day restarted car no problem but knock was still there. Greater the revs the louder the knock. I was advised to clean the injectors which I did but made no difference, it seemed the noise was coming from tapit cover so I removed the head but all looks ok, valves not stuck or gummed up, what would you advise I do next